GitLab

* fel: Add the ability to pass uEnv-style data via FEL

The corresponding format is recognized by having the environment
data (= text) start with a special "#=uEnv" marker. Upon transfer
of such a file, sunxi-fel will detect this condition, and set a
field in the SPL header accordingly - which in turn also requests
U-Boot to auto-import it (i.e. merge with the default environment).

(Note that this requires a U-Boot version that knows about the
new meaning of this field, namely v2016.09 or later. Older U-Boot
versions will fail to import the uEnv-style data.)
Signed-off-by: Bernhard Nortmann <bernhard.nortmann@web.de>